The multimedia interfaces, such as HDMI/Micro USB/Display port/UDI, of various electrical connectors are high frequency interfaces in the industry. HDMI can provide data transfer bandwidth as high as 10.2 Gbps, Micro USB 5.1 Gbps, and UDI even higher: 21 Gpbs. HDMI can transfer uncompressed audio messages and HD video signals, and does not need to have D/A or A/D switch before signal delivery, which can guarantee the high quality of audio and visual signals.
However, the interfacing internal core wire and the terminal is welded manually, one core wire welded each time. The efficiency is low, the quality is not steady, and the tin spots emerged from welding vary in size. Also, the spacing between the wire connecting terminals in the interface is too narrow, so it is hard to weld them and electrical connectors' short circuit and housing scalding can occur easily. The high-frequency transfer performance of the electrical connector is not steady and the yield rate is low.
A Chinese patent of a High Definition Digital Interface and its Processing Technology, Publication Patent Number being CN1841857, offers a technology of automatically welding the electrical connector. The steps are as this: assemble the electrical connector first, smear the solder paste, and then place the connector in the wire fixture, and heat up the wire fixture. As the wire fixture temperature rises, the solder paste melts, and the core wire is automatically welded with the corresponding wire connecting terminals in the electrical connector. However, the wire fixture transfers the heat in a low speed and it is low in processing efficiency. The welding effect is not satisfactory. It is needed to heat up the whole wire fixture for the welding, which consumes a large amount of energy, thus resulting in high production costs. It cannot meet the current demand for energy saving, nor can it sustain continuous production or high production efficiency.
Another Chinese patent of Processing Technology of High Definition Digital Interface, with Publication Patent Number of CN1976421, proposes a brand-new automatic welding process. The applicant also provides an automatic welding machine, through which the electrical connector can be welded automatically. In this process, the electrical connector is assembled first, and the solder paste is smeared in the wire connecting terminal, and then a C-shaped retaining clip is used to clamp each core wire, afterwards, set the electrical connector on the fixture of supply belt. The belt delivers all electrical connectors pending for welding in the automatic welding zone. A lamp able to emit heating light is set in the automatic welding zone of the automatic welding machine. The heating light radiates through a slot from the automatic welding machine, shining on the wire connecting terminal in the electrical connector, which melt the solder paste. The melted solder paste connects the core wire with its corresponding wire connecting terminal. However, the rays from the lamp, i.e.: infrared rays 72, are scattering. To avoid the rays from heating up unnecessary areas other than the electrical connector, the automatic welding machine obstructs the infrared rays from coming in, set with a beam stopper to absorb the infrared rays. A small slot is reserved in the beam stopper to allow for part of the rays to shine in. Most of the rays shine on the stopper whose purpose is only to form that slot, and it wastes most energy.
Since only a small portion of infrared rays emitted from the lamp shine through the slot, there is even a smaller portion of rays shining on the solder paste. The rays are severely insufficient. Thus, the heating period must be prolonged to make up for it. There are also the following disadvantages to this process:
(1), The heating by infrared rays during the irradiation is not even, and the heat exposure of solder paste is not even, which can result in bad solder paste melting and some tin balls in the tin spots, lowering the electric performance of welding spots.
(2), Welding spots on two sides of the electrical connector are, in particular, affected by the uneven heating. Due to the scarce heating on both sides of the connector, bad melting, tack welding in particular, can easily occur.
(3), During this welding process, the solder paste is slowly heated up till melting and then cools down and become solidified slowly, which can cause defects of various kinds in the internal structure of the welding spots formed by solder paste. Water, either in large amount or not, is unavoidable within the solder paste. Without drying out the water within, air cavities may appear in the welding spots when welding is completed. This can cause great resistance, poor electric performance and even tack welding to the welding spots.
(4), The automatic welding machine heats up slowly. The metallic clips and core wires absorb heat fast and their temperature is high. It can easily scald the housing and the core wires.
(5), The infrared rays are not concentrated. The section that needs heating cannot receive sufficient infrared rays. For example, the solder paste in the solder cup is not heated sufficiently. Nevertheless, other zones that do not need heating receive the infrared rays, such as the housing. Heated by infrared rays, the housing melts which affects the quality and outlook of the electrical connector and produces defective products easily.